Anvil from Guru blender not exporting with all materials and textures to glb file for WebGL
glTF 2.0 has a specific PBR material model, for transfer to realtime rendering engines.  It cannot support arbitrary arrangements of Blender nodes, as WebGL wouldn't be able to handle realtime rendering of arbitrarily complex Blender nodes.  Instead, the glTF material definition has a strict number of fields, corresponding to a particular interpretation of physically-based materials.
The Blender Manual documents how to export materials to glTF.  The short version is, you'll need to adapt your material node setup to use primarily images connected to the Principled BSDF node.